Surface-Mounted Light-Emitting Device and Fabrication Method Thereof

ABSTRACT

A surface-mounted light-emitting device is fabricated by epitaxial growth: forming the LED epitaxial structure over a growth substrate through epitaxial growth; chip fabrication: determining P and N electrode regions and an isolating region over the LED epitaxial structure surface and fabricating the P and N electrode pads and the insulator over the P and N electrode regions and the isolating region, wherein the P and N electrode pads have sufficient thicknesses to support the LED epitaxial structure, and the insulator is formed between the P and N electrode pads to prevent the P and N electrode pads from a short circuit; removing the growth substrate and unitizing the LED epitaxial structure to form the chip; and SMT packaging: providing the supporting substrate and directly mounting the P and N electrode pads of the chip over the supporting substrate through SMT packaging to thereby form the surface-mounted LED light-emitting device.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of, and claims priority to,U.S. patent application Ser. No. 14/748,701 filed on Jun. 24, 2015,which in turn is a continuation of, and claims priority to,PCT/CN2014/071079 filed on Jan. 22, 2014, which claims priority toChinese Patent Application No. 201310195976.4 filed on May 24, 2013. Thedisclosures of these applications are hereby incorporated by referencein their entirety.

BACKGROUND

Surface-Mounted Technology (SMT) packaging is widely applied in existingLED light-emitting device, as shown in FIG. 1, to reduce thermalresistance of the device and to improve device stability; as inconventional method, conventional LED chip 100 is placed in thepackaging body 120 and a pin 110 is led from the packaging body to makeit directly mounted over the target board, e.g., PCB; in addition,phosphor may be coated over the packaging body to form a mixed-colorlight-emitting device. The SMT soldering method comprises eutecticsoldering and reflow soldering.

SUMMARY

The present disclose provides a surface-mounted light-emitting deviceand fabrication thereof, which, in structure, changes conventional SMTpackage type by directly mounting the chip over the supporting substratethrough an electrode pad. In addition, in terms of fabrication method,soldering is followed after the chip process without package step, whichis mainly applicable to flip-chip LED device.

According to a first aspect of the present disclosure: a light emittingdiode chip applicable to SMT is provided, comprising: a LED epitaxialstructure having two opposite surfaces, in which, the first surface is alight-emitting surface; P and N electrode pads over the second surfaceof the epitaxial structure, which have sufficient thickness to supportthe LED epitaxial structure, and the P and N electrode pads have twoopposite surfaces respectively, in which, the first surface isapproximate to the LED epitaxial structure; an insulator between the Pand N pads to prevent the P and N electrode pads from short circuit; andthe P and N electrode pads are directly applied in the SMT package.

According to a second aspect of the present disclosure, asurface-mounted LED light-emitting device is provided, comprising a chipstructure and a supporting substrate, in which, the chip structurecomprises: a LED epitaxial structure having two opposite surfaces, inwhich, the first surface is a light-emitting surface; P and N electrodepads over the second surface of the epitaxial structure, which havesufficient thickness to support the LED epitaxial structure, and the Pand N electrode pads have two opposite surfaces respectively, in which,the first surface is approximate to the LED epitaxial structure; aninsulator between the P and N pads to prevent the P and N electrode padsfrom short circuit; and the chip is directly mounted over the supportingsubstrate via the P and N electrode pads through SMT package.

According to a third aspect of the present disclosure, a fabricationmethod of a surface-mounted LED light-emitting device is provided,comprising: 1) epitaxial growth: form a LED epitaxial structure over thegrowth substrate through epitaxial growth; 2) chip fabrication:determine P and N electrode regions and an isolating region over the LEDepitaxial structure surface and fabricate P and N electrode pads and aninsulator in each region, in which, the P and N electrode pads havesufficient thickness to support the LED epitaxial structure, and theinsulator is formed between the P and N pads to prevent the P and Nelectrode pads from short circuit; remove the growth substrate andsimplify the LED epitaxial structure to form a LED chip; 3) SMT package:provide a supporting substrate and directly mount the P and N electrodepads of the LED chip over the supporting substrate through SMT packageto finally form a surface-mounted LED light-emitting device.

Specifically, the LED epitaxial structure is a flip-chip film structure.In some embodiments, a patterned passivating layer can be fabricatedover the film LED surface. In some embodiments, phosphor can be coatedover the film LED surface.

The P and N electrode pads have sufficient thickness to support the LEDepitaxial structure. In some embodiments, the P electrode pad is thickerthan 50 μm and the N electrode pad is also thicker than 50 μm. In someembodiments, the P and N electrode pads cover more than 80% of theentire luminous region and the remaining area is the insulatorstructure.

A gap D is formed between the P and N electrode pads. The insulatorfills in the gap between the P and N electrode pads, and preferably, theinsulator and the P and N electrode pads are closely jointed (basically,with no gap) to guarantee physical support of the epitaxial structure.In some embodiments, the insulator has two opposite surfaces, in which,the first surface is approximate to the LED epitaxial structure and thesecond surface extrudes beyond either second surface of the P and Nelectrode pads. The insulator extrudes the second surface of theelectrode pad, which effectively avoids short circuit of the P and Nelectrodes in later SMT process of the chip. In some embodiments, thelower surface of the P and N electrode pads are at same level. It isassumed that height difference between lower surfaces of the P and Nelectrode pads and that of the insulator is H; and gap between the P andN electrode pads is D and H/D is 0.5-2. In some embodiments, gap Dbetween the P and N electrode pads is 20-150 μm. In some embodiments,melting point or softening point of the insulator is lower than meltingpoints of the P and N electrode pads and the insulator can be made ofcolloid material like SU8, BCB or dry film. In some embodiments, heightdifference H between lower surface of the insulator and those of the Pand N electrode pads is 20 μm-150 μm.

The P and N electrode pads and the insulator basically cover the entiresurface of the LED epitaxial structure. In some embodiments, edges ofthe P and N electrode pads are beyond that of the LED epitaxialstructure with a certain distance to prevent the solder paste fromclimbing up the epitaxial layer due to solder paste backflow during chipSMT package, which may result in electric leakage of the device.Preferably, it is assumed that distance between edges of the P and Nelectrode pads are beyond that of the LED epitaxial structure is D, andminimum thickness of the P and N electrode pads is T, and D/T is 0.5-2.It is assumed that area of the epitaxial film layer is S1 and area ofthe pad layer that is beyond the epitaxial layer area is S2, and theratio between S1 and S2 is ½-3/1, which is preferably 9/5. In someembodiments, distance that edges of the P and N electrode pads arebeyond the LED epitaxial structure edge equals to or is larger than 30um.

In some light-emitting devices of larger size, one important factor thatinfluences device reliability is shape and size of the P and N electrodepads. For example, in a known asymmetric electrode design, large areadifference of electrodes may lead to chip inclination during eutecticprocess, resulting in eutectic failure at electrodes of small areas andcausing final electric connection failure. Therefore, for light-emittingdevices of larger size, area ratio between the P and N electrode pads ispreferably 6:4-1:1 (this ratio shall not restrict that the P electrodepad is larger than the N electrode pad) and most preferably, areas ofthe P and N electrode pads are same. In some embodiments, at least twoinsulating layers and one conducting layer are arranged between the Pand N electrode pads and the LED epitaxial structure, in which, in thefirst insulating layer and the conducting layer, current is uniformlyinjected to the LED epitaxial structure, and in the second insulatinglayer, areas of the P and N electrode pads are basically same.

The light emitting diode chip applicable to SMT can be obtained by (butnot restrictive to) the steps below: 1) provide a growth substrate, overwhich, grow a buffer layer, an N-type epitaxial layer, a light-emittinglayer and a P-type epitaxial layer in successive; 2) pattern theepitaxial layer and etch part of the epitaxial layer to expose theN-type epitaxial layer; 3) form a high-reflectivity P-type ohmic contactlayer over the P-type epitaxial layer and an N-type ohmic contact layerover the N-type epitaxial layer; 4) form an insulation paste isolatinglayer between the P-type ohmic contact layer and the N-type ohmiccontact layer; 5) electroplate the P and N electrode pads to form anelectroplating layer capable for supporting the epitaxy; 6) remove thegrowth substrate to expose the buffer epitaxial layer and determinegrain size, and etch the epitaxial layer outside the determined regiontill the ohmic contact layers are exposed; 7) form a passivating layerover the buffer epitaxial layer and roughen its surface; and 8) coatphosphor material over the grain surface to form a fixed-color luminouschip, which can be directly applied in SMT mounting.

In some embodiments, when the LED chip is directly applied in SMT step,the supporting substrate surface is coated with a solder layer withthickness smaller or equaling to height difference between the secondsurface of the insulator and either second surface of the P and Nelectrode pads. The insulator is made of insulating colloid. Press theinsulating colloid when the chip is aligned with the supportingsubstrate to further guarantee electric isolation between the P and Nelectrode pads during reflow soldering.

The fabrication method of the surface-mounted LED light-emitting deviceof the present disclosure simplifies conventional LED chip packageprocess in SMT, i.e., after step 2), a special-structure chip is formedand directly soldered over the supporting substrate without packaging.In some embodiments, during chip fabrication, after the growth substrateis removed, etch the LED epitaxial structure to form a cutting path, andphysically cut the electrode pads over the cutting path to ensure thatedges of the P and N electrode pads are beyond that of the LED epitaxialstructure with a certain distance, thereby forming a series of LEDchips.

The LED light-emitting device and fabrication method thereof disclosedin the present disclosure emits pre-package of the LED chip inconventional SMT process and saves much costs; in comparison toconventional flip chip, it is more reliable during reflow soldering;moreover, the conventional flip chip has no supporting substrate and thegrowth substrate can be hardly removed; in contrast, this LEDlight-emitting device can support the epitaxy thanks to thickelectroplating pads and the growth substrate can be removed to improveluminous effect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simple structure diagram of a conventional SMTlight-emitting device.

FIG. 2 is a structural section view according to Embodiment 1 of thepresent disclosure.

FIG. 3 is a structural section view according to Embodiment 2 of thepresent disclosure.

FIG. 4 is a structural section view according to Embodiment 3 of thepresent disclosure.

FIG. 5 illustrates sectional views of a device structure according toEmbodiment 4 of the present disclosure;

FIG. 6 illustrates another sectional view.

FIG. 7 is a structural section view according to Embodiment 5 of thepresent disclosure.

FIG. 8 shows a SMT light-emitting device fabricated from the lightemitting diode chip according to FIG. 7.

FIG. 9 illustrates a first step in the fabrication of the light-emittingdevice as shown in FIG. 7;

FIG. 10 illustrates a second step;

FIG. 11 illustrates a third step;

FIG. 12 illustrates a fourth step;

FIG. 13 illustrates a fourth step;

FIG. 14 illustrates a fifth step;

FIG. 15 illustrates a sixth step;

FIG. 16 illustrates a seventh step;

FIG. 17 illustrates an eighth step.

DETAILED DESCRIPTION

References will be made to the following drawings to give cleardescription of the LED device structure and fabrication method,including the preferred embodiments. It is to be understood that bythose skilled in the art that various changes may be made thereinwithout influencing the beneficial effects of the present disclosure.Therefore, the descriptions below shall be understood as widely known bythose skilled in the art and are not meant to limit the scope of theinvention.

According to some embodiments, a SMT light-emitting device andfabrication method thereof are provided by directly mounting the lightemitting diode chip over the supporting substrate. In device structure,the P and N electrode pads of the chip have enough thickness to supportthe epitaxial structure, and an insulator with a lower surface lowerthan either lower surface of the P and N electrode pads is arrangedbetween the P and N electrode pads, which supports the LED epitaxialstructure and prevents the P and N electrode pads from short circuitwhen the chip is applied in soldering. In fabrication method, solderingis followed after the chip process without package step.

A detailed description will be given to the SMT light-emitting deviceand fabrication method.

Embodiment 1

With reference to FIG. 2, a light emitting diode chip 200 applicable toSMT, comprising a luminous epitaxial laminated layer 210, ohmic contactlayers 221, 222, electrode pads 231, 232 and an insulator 230. Theluminous epitaxial laminated layer 210 is a flip-chip film structure,which from up to bottom comprises an N-type epitaxial layer, alight-emitting layer and a P-type epitaxial layer. However, it is notlimited to the layers aforesaid. The N-type ohmic contact layer 221 andthe P-type ohmic contact layer 222 are over the N-type epitaxial layerand the P-type epitaxial layer respectively with parallel lowersurfaces, which may be made of Cr, Au, Ti, Ni, Ag, Pt or TiW or any oftheir combinations. As a preferred embodiment, a multi-layer structureof high-reflectivity metal material is provided for ohmic contact andmirror reflection at the same time. The P and N electrode pads 232 and231, more than 50 μm thick, are over the P and N-type ohmic contactlayers respectively, to support the flip-chip film structure 210, andthe preferred thickness is 70-150 μm. The P and N electrode pads 232 and231 can be made of Ti, Ni, Cu, Au, AuSn, SnCu, SnBi, AgSnCu or any oftheir combinations. The insulator 230 is between the P and N electrodepads 232 and 231 and fills in the gap between the N-type ohmic contactlayer 221 and the P-type ohmic contact layer 222, in which, the lowersurface, of stepped shape, is lower than those of the P and N electrodepads 232, 231 and is made of permanent insulating colloid like SU8, BCB,dry film, etc. As a preferred embodiment, the epitaxial layer surface iscovered with a passivating layer 240 made of silicon nitride or siliconoxide.

In this embodiment, the P and N electrode pads have two functions: oneis to support the LED epitaxial structure with sufficient thickness andarea, in which, preferably, the area accounts for at least 80% of theepitaxial layer and the remaining area is insulator material; the secondfunction is for direct application in the SMT package. To realize theaforesaid two functions, it is necessary to guarantee completeness ofphysical support of the LED epitaxial structure and to prevent the P andN electrode pads from short circuit at the same time. Therefore, the Pand N electrode pads and the insulator basically cover the entiresurface of the LED epitaxial structure and are closely jointed(basically, with no gap) to ensure completeness of the epitaxialstructure support and to effectively avoid damage of the flip-chipepitaxial film. The insulator 230 extrudes the lower surface of theelectrode pad, which effectively avoids short circuit of the P and Nelectrodes in later SMT process of the chip. Lower surfaces of the P andN electrode pads are at same level. It is assumed that height differencebetween the relative position of the lower surfaces of the electrodepads and that of the lower surface of the insulator is H and the gapbetween the P and N electrode pads is D, and implementation effect ofthe present embodiment can be optimized by adjusting H and D. In thisembodiment, gap D between the P and N electrode pads is 20-150 μm, andheight difference H is 20 μm-150 μm.

Embodiment 2

With reference to FIG. 3, this embodiment differs from Embodiment 1mainly in that: Edges of the P and N electrode pads 232 and 231 arebeyond that of the LED epitaxial structure 210 with a certain distanceto prevent the solder paste from climbing up the epitaxial layer due tosolder paste backflow during chip SMT package, which may result inelectric leakage of the device. It is assumed that distance betweenedges of the P and N electrode pads are beyond that of the LED epitaxialstructure is D, and minimum thickness of the P and N electrode pads isT. In general, as T increases, D increases accordingly, and in apreferred embodiment, D/T ratio is 0.5-2. It is assumed that area of theLED epitaxial structure 210 is S1 and area of the P and N electrode padsthat is beyond the epitaxial layer is S2, and S1/S2 ratio is ½-3/1, andpreferably 9/5. The above parameter ranges are only for reference andshall not be constructed as limitation of the present disclosure.

Embodiment 3

In some light-emitting devices of larger size, one important factor thatinfluences device reliability is shape and size of the P and N electrodepads. For example, in a known asymmetric electrode design, large areadifference of electrodes may lead to chip inclination during eutecticprocess, resulting in eutectic failure at electrodes of small areas andcausing final electric connection failure.

With reference to FIG. 4, difference between this embodiment andEmbodiment 2 is that: the P and N electrode pads have approximate orbasically same areas. Specifically, an insulating layer 250 is arrangedbetween the P and N ohmic contact layers 232 and 231 to enable electricisolation between the N-type ohmic contact layer 231 and thelight-emitting layer and the p-type semiconductor of the LED epitaxialstructure. Open holes at positions of the insulating layer 250corresponding to the P and N ohmic contact layers. The P and N electrodepads fill through this opening structure and contact with the P and Nohmic contact layers respectively.

Embodiment 4

This embodiment optimizes the current injection structure of the LEDepitaxial layer and differs from Embodiment 3 in that: a dual insulatinglayer and a conducting layer structure are arranged between the P and Nohmic contact layers and the P and N electrode pads, in which, in thefirst insulating layer and the conducting layer, current is uniformlyinjected to the LED epitaxial structure, and in the second insulatinglayer, areas of the P and N electrode pads are basically same. Withreference to FIG. 5 and FIG. 6, in which, FIG. 6 is a section view alongthe first insulating layer 251. In the central regions of the LEDepitaxial structure 210, open a plurality of first opening structuresthat pass through the P-type epitaxial layer, the light-emitting layerand till the N-type epitaxial layer; cover an ohmic contact layer 220over the P-type epitaxial layer surface and cover the first insulatinglayer 251 over the ohmic contact layer 220 and also the side wall of theopening structure to expose the N-type epitaxial layer; open at leastone second opening structure at the position of the first insulatinglayer 251 corresponding to the ohmic contact layer 220; fabricate theconducting layer, which is divided into an N conducting region 261 and aP conducting region 262, over the first insulating layer 251, in which,the N conducting region 261 contacts with the N-type epitaxial layerthrough the first opening structure and P conducting region 262 contactswith the ohmic contact layer 220 through the second opening structure;fabricate a second insulating layer 252 over the conducting layer andopen a third opening structure at positions corresponding to the Nconducting region 261 and the P conducting region 262, in which, the Pand N electrode pads 232 and 231 fill in this opening structure andcontact with the P and N conducting regions over the conducting layerrespectively.

Embodiment 5

With reference to FIG. 7, this embodiment differs from Embodiment 2mainly in that: the LED epitaxial structure surface is covered with apassivating layer 240 and a phosphor layer 250 is coated over thelight-emitting surface. As a preferred embodiment, the light-emittingsurface may be roughened.

With reference to FIG. 8, a SMT light-emitting device fabricated fromthe light emitting diode chip as shown in FIG. 7. The fabrication methodcomprises three processes: epitaxial growth, chip fabrication and SMTsoldering. This fabrication of the SMT light-emitting device will bedescribed in detail with reference to FIGS. 9-17.

First step is epitaxial growth. Specifically: provide a growth substrate201, over which, form a buffer layer, an N-type epitaxial layer, alight-emitting layer and a P-type epitaxial layer in successive, andthis epitaxial laminated layer is 210, as shown in FIG. 9. This step canadopt conventional epitaxial growth process like MOCVD.

Next step is chip fabrication, comprising mesa etching, fabrication ofohmic contact layer, insulator and electrode pad and simplificationtreatment. Specifically: 1) pattern the epitaxial layer 210 throughyellow-light photolithography technology and etch part of the epitaxiallayer through ICP dry etching to expose the N-type epitaxial layer withetching depth about 1 μm; 2) evaporate a high-reflectivity P-type ohmiccontact layer 222 through vacuum electron beam over the P-type epitaxiallayer and the metal layer may comprise any one or several of Cr, Ag, Ni,Al, Pt, Au, Ti, TiW with total thickness not more than 0.5 μm andpreferred thickness of 1 μm; form an N-type ohmic contact layer 221 overthe N-type epitaxial layer and the metal layer may comprise any one orseveral of Cr, Ag, Ni, Al, Pt, Au, Ti, TiW with total thickness not morethan 1.5 μm and preferred thickness of 2 μm; the two contact metalsalways keep same height, as shown in FIG. 10; 3) form a dry-filmphotoresist isolating layer as the insulator 230 between the P-typecontact layer and the N-type contact layer through dry film photoresistprocess with height not less than 70 μm and preferred height of 120 μm,as shown in FIG. 11; 4) electroplate a thick P-type electrode pad layer232 over the P-type ohmic contact layer 222 and a thick N-type electrodepad layer 231 not less than 50 μm thick over the N-type ohmic contactlayer 221 through electroplating with material of Ni, Cu, Au, Ag orother metal material eutectic melt with Sn and form an electroplatinglayer capable for supporting the epitaxy, as shown in FIG. 12; 5) removethe growth substrate 201 through laser lifting-off to expose theepitaxial layer; determine each grain size through yellow-lightphotolithography and etch the epitaxial layer outside the determinedregion through ICP dry etching until the P-type ohmic contact layer 222and the N-type ohmic contact layer 221 are exposed, as shown in FIG. 13;6) based on chip size, etch the LED epitaxial structure to form acutting path through dry etching or wet etching; 7) form a passivatinglayer 240, made of S1 oxide or nitride, over the exposed epitaxial layerand form a nano-scale roughening structure over the surface through dryetching or wet etching, as shown in FIG. 15; 8) coat phosphor material250 over the grain surface through the phosphor coating technology; and9) physically cut the electrode pad layer along the cutting path tosimplify the luminous structure and form the LED chip. And the chipfabrication step is finished. As shown in FIG. 16, the LED chip can bedirectly applied in SMT.

Lastly, pack the fabricated LED chip fabricated over a supportingsubstrate with conventional SMT soldering step. Specifically: 1) providea supporting substrate and place the solder paste in specific region ofthe supporting substrate through metal stencil printing or silk-screenprinting, in which, the specific region has P and N joints; 2) place theaforesaid LED chip over the supporting substrate to make the P and Nelectrode pads correspond to the P and N joints over the supportingsubstrate; 3) place the supporting substrate well-placed over the LEDinto the reflow soldering equipment for reflow soldering so as to form asurface-mounted LED light-emitting device, in which, the supportingsubstrate is MCPCB structure; reflow soldering temperature is 280-320°C.; the solder paste is thicker than 30 μm and the metal stencilprinting or silk-screen printing is thicker than the solder paste.

In this embodiment, height from which the insulator 230 extrudes the Pand N electrode pads is larger than the solder paste thickness, whichensures electric isolation between the P and N electrode pads duringreflow soldering when the chip is aligned with the supporting substrate.

In this embodiment, etch the LED epitaxial structure to form a cuttingpath, and physically cut the electrode pads over the cutting path toensure that edges of the P and N electrode pads are beyond that of theLED epitaxial structure with a certain distance, thereby forming aseries of LED chips.

This embodiment emits pre-package of the LED chip in conventional SMTprocess and saves much costs; in comparison to conventional flip chip,it is more reliable during reflow soldering; moreover, the conventionalflip chip has no supporting substrate and the growth substrate can behardly removed; in contrast, this LED light-emitting device can supportthe epitaxial layer thanks to thick electroplating pads and the growthsubstrate can be removed to improve luminous effect.

All references referred to in the present disclosure are incorporated byreference in their entirety. Although specific embodiments have beendescribed above in detail, the description is merely for purposes ofillustration. It should be appreciated, therefore, that many aspectsdescribed above are not intended as required or essential elementsunless explicitly stated otherwise. Various modifications of, andequivalent acts corresponding to, the disclosed aspects of the exemplaryembodiments, in addition to those described above, can be made by aperson of ordinary skill in the art, having the benefit of the presentdisclosure, without departing from the spirit and scope of thedisclosure defined in the following claims, the scope of which is to beaccorded the broadest interpretation so as to encompass suchmodifications and equivalent structures.

1. A method of fabricating a surface-mounted light-emitting diode (LED)light-emitting device, the method comprising: 1) epitaxial growth: forman LED epitaxial structure over a growth substrate through epitaxialgrowth; 2) chip fabrication: determine P and N electrode regions and anisolating region over the LED epitaxial structure surface and fabricateP and N electrode pads and an insulator over the P and N electroderegions and the isolating region, wherein the P and N electrode padshave sufficient thicknesses to support the LED epitaxial structure, andthe insulator is formed between the P and N electrode pads to preventthe P and N electrode pads from a short circuit; remove the growthsubstrate and unitize the LED epitaxial structure to form a LED chip; 3)SMT packaging: provide a supporting substrate and directly mount the Pand N electrode pads of the LED chip over the supporting substratethrough SMT packaging to thereby form a surface-mounted LEDlight-emitting device.
 2. The method of claim 1, wherein in step 2), theformed insulator has opposite a first insulator surface and a secondinsulator surface, wherein the first surface is adjacent to the LEDepitaxial structure and the second surface extrudes beyond either of thesecond electrode surfaces of the P and N electrode pads to prevent the Pand N electrode pads from short circuiting when directly applied in theSMT packaging.
 3. The method of claim 2, wherein in step 2), a meltingpoint or softening point of the insulator material is lower than meltingpoints of the P and N electrode pads.
 4. The method of claim 2, whereinin step 3), the supporting substrate has a surface coated with a solderlayer with a thickness smaller than or equal to a height differencebetween the second insulator surface and either of the second electrodesurfaces of the P and N electrode pads, wherein the insulator extendsthrough the solder layer and is in contact with the solder layer and thesupporting substrate, wherein a distance between edges of the P and Nelectrode pads beyond that of the LED epitaxial structure is D, aminimum thickness of the P and N electrode pads is T, and wherein D/T is0.5-2.
 5. The method of claim 1, wherein the insulator comprises acolloid material.
 6. The method of claim 1, wherein in step 2), afterthe growth substrate is removed, the method further comprising etchingthe LED epitaxial structure to form a cutting path, and physicallycutting the electrode pads over the cutting path to ensure that edges ofthe P and N electrode pads are beyond an edge of the LED epitaxialstructure with a specified distance, thereby forming a series of LEDchips.
 7. The method of claim 1, wherein in step 3), the P and Nelectrode pads of the LED chip are connected to the supporting substratethrough reflow soldering.
 8. A surface-mounted light-emitting diode(LED) light-emitting device, comprising a chip and a supportingsubstrate, wherein the chip comprises: an LED epitaxial structure havingopposite a first surface and a second surface, wherein the first surfaceis a light-emitting surface; P and N electrode pads over the secondsurface of the epitaxial structure, which has a sufficient thickness tosupport the LED epitaxial structure, and the P and N electrode pads eachhave opposite a first electrode surface and a second electrode surface,respectively, wherein the first electrode surface is adjacent to the LEDepitaxial structure; an insulator between the P and N electrode pads toprevent the P and N electrode pads from a short circuit; and wherein thechip is directly mounted over the supporting substrate via the P and Nelectrode pads through SMT packaging; and wherein the light-emittingdevice is fabricated using a method comprising: 1) epitaxial growth:forming the LED epitaxial structure over a growth substrate throughepitaxial growth; 2) chip fabrication: determining P and N electroderegions and an isolating region over the LED epitaxial structure surfaceand fabricating the P and N electrode pads and the insulator over the Pand N electrode regions and the isolating region, wherein the P and Nelectrode pads have sufficient thicknesses to support the LED epitaxialstructure, and the insulator is formed between the P and N electrodepads to prevent the P and N electrode pads from a short circuit;removing the growth substrate and unitizing the LED epitaxial structureto form the chip; 3) SMT packaging: providing the supporting substrateand directly mounting the P and N electrode pads of the chip over thesupporting substrate through SMT packaging to thereby form thesurface-mounted LED light-emitting device.
 9. The light-emitting deviceof claim 8, wherein the insulator has opposite a first and a secondinsulator surfaces, wherein the first insulator surface is adjacent tothe LED epitaxial structure and the second insulator surface extrudesbeyond either of the second electrode surfaces of the P and N electrodepads to prevent the P and N electrode pads from a short circuit whendirectly applied in the SMT package, wherein the light-emitting devicefurther comprises a solder layer in contact with and between thesupporting substrate and the P and N electrode pads; and wherein theinsulator extends through the solder layer and is in contact with thesolder layer and the supporting substrate.
 10. The light-emitting deviceof claim 9, wherein a melting point or softening point of the insulatoris lower than melting points of the P and N electrode pads.
 11. Thelight-emitting device of claim 9, wherein the insulator comprises acolloid material.
 12. The light-emitting device of claim 9, wherein aheight difference between the second insulator surface and either of thesecond electrode surfaces of the P and N electrode pads is 20 μm-100 μm.13. The light-emitting device of claim 8, wherein edges of the P and Nelectrode pads are beyond that of the LED epitaxial structure to serveas a supporting structure of the epitaxial structure.
 14. Thelight-emitting device of claim 13, wherein a distance that edges of theP and N electrode pads are beyond that of the LED epitaxial structure isequal to or larger than 30 μm to prevent a side wall of LED epitaxialstructure from short circuit when the P and N electrode pads aredirectly mounted over the supporting substrate via SMT soldering. 15.The light-emitting device of claim 8, wherein the second electrodesurfaces of the P and N electrode pads are at the same level.
 16. Thelight-emitting device of claim 8, wherein a gap between the P and Nelectrode pads is 20-150 μm.
 17. The light-emitting device of claim 8,wherein the P and N electrode pads are thicker than 50 μm to support theLED epitaxial structure.
 18. The light-emitting device of claim 8,wherein areas of the P and N electrode pads are substantially same. 19.The light-emitting device of claim 8, wherein the P and N electrode padsand the insulator cover an entire surface of the LED epitaxialstructure.
 20. The light-emitting device of claim 8, wherein the P and Nelectrode pads and the insulator are closely jointed.